How to Find the CFM of a Squirrel Cage Fan 
Here’s how to find the CFM of a squirrel cage fan? CFM is the cubic foot per minute of air movement, and it is calculated by dividing the fan’s velocity by the square footage of the opening. However, calculating the fan’s CFM is not that simple, and you will need a pitot tube manometer or a vane anamometer, as well as a set of conversion tables to get the right answer.
Calculating velocity
To calculate the velocity of a squirrel cage fan, you should first know how much force it requires to turn the blades. The velocity of a fan is measured in feet per second (fpm) and is expressed in units of one-half the axial velocity. If the fan is driven by a dc separately excited motor, the motor speed will be 500 rpm. The motor torque is assumed to be constant.
The rotor size of a squirrel cage fan is an important parameter that will determine its performance. The average diameter of the fan casing, including the rotor, is an important parameter. This factor affects the aerodynamic flow inside the fan. A large volute can make a squirrel cage fan less efficient. Combined with the size of the squirrel cage, the axial gap will determine how effective the fan is.
The rpm and the diameter of a squirrel cage fan will affect the cfm produced. Considering that different squirrel cage fans will have slightly different CFM ratings, you need to know both the diameter and rpm of the fan to find the correct CFM rating. You can also compare similar fans to determine what their CFM rating is. This way, you can be sure that the fan you’re buying can produce the necessary amount of air.
Calculating cfm
The area of the opening in square feet and the rpm of the fan are the two primary factors to consider in calculating CFM. The cfm of a squirrel cage fan will vary widely based on the size, rpm, and overall capacity of the duct. A good source for CFM is WW Grainger. If you’re not familiar with their catalogs, they provide detailed information on air movement and the capacity of different types of fans.
There are several ways to calculate CFM. A simple way to calculate CFM is to divide the incoming air volume by the outgoing compressed air volume. A radial vane rotor of 18 inches dia. fits inside an old fan housing and works at 3550 rpm. In this way, the radial vane fan can move a large volume of air. The resulting volume of air can be measured with a thermometer.
Calculating cfm at a 90 degree elbow
If you are installing a squirrel cage fan at a 90-degree elbow, you should know how to calculate its cfm. The reason behind this is due to the system effect. When two elements are close to each other, the energy and pressure in the system increase. You can use this rule of thumb to calculate the cfm of the fan and then compare it to its measured value.
How do you calculate the CFM of a squirrel cage fan?
Answer: The CFM of a squirrel cage fan can be calculated by multiplying the fan RPM by the fan blade tip speed.
Why is it important to know the CFM of a squirrel cage fan?
Answer: It is important to know the CFM of a squirrel cage fan because the CFM determines the amount of air flow the fan is able to produce.
What are the factors that affect the CFM of a squirrel cage fan?
Answer: The CFM of a squirrel cage fan is affected by the fan RPM and the fan blade tip speed.
How does the CFM of a squirrel cage fan compare to other types of fans?
Answer: The CFM of a squirrel cage fan is typically higher than other types of fans.
What are some applications that require high CFM squirrel cage fans?
Answer: Some applications that require high CFM squirrel cage fans include industrial process cooling evaporative cooling and HVAC systems.
How can the CFM of a squirrel cage fan be increased?
Answer: The CFM of a squirrel cage fan can be increased by increasing the fan RPM or the fan blade tip speed.
Is there a limit to how high the CFM of a squirrel cage fan can be?
Answer: Yes there is a limit to how high the CFM of a squirrel cage fan can be.
The maximum CFM is determined by the fan RPM and the fan blade tip speed.
What happens if the CFM of a squirrel cage fan is too high?
Answer: If the CFM of a squirrel cage fan is too high it can cause the fan to overheat and eventually fail.
What are the consequences of having too low of a CFM for a squirrel cage fan?
Answer: If the CFM of a squirrel cage fan is too low it will not be able to move enough air to meet the needs of the application.
This can lead to decreased performance or even damage to the equipment.
How often should the CFM of a squirrel cage fan be checked?
Answer: The CFM of a squirrel cage fan should be checked on a regular basis to ensure it is within the proper range.
How can you tell if the CFM of a squirrel cage fan is too high or too low?
Answer: The CFM of a squirrel cage fan can be checked with a manometer or an airflow meter.
What is the difference between a manometer and an airflow meter?
Answer: A manometer measures the pressure of the air while an airflow meter measures the volume of air.
Can the CFM of a squirrel cage fan be adjusted?
Answer: Yes the CFM of a squirrel cage fan can be adjusted by changing the fan RPM or the fan blade tip speed.
What should be done if the CFM of a squirrel cage fan is not within the proper range?
Answer: If the CFM of a squirrel cage fan is not within the proper range the fan should be adjusted or replaced.
What are the dangers of having a squirrel cage fan with an incorrect CFM?
Answer: Dangers of having a squirrel cage fan with an incorrect CFM include decreased performance damage to the equipment and even personal injury.
Jessica Watson is a PHD holder from the University of Washington. She studied behavior and interaction between squirrels and has presented her research in several wildlife conferences including TWS Annual Conference in Winnipeg.
